As a point-to-multipoint fiber access technology, a PON is composed of an OLT at the central office, an ONU at the customer premises, and an Optical Distribution Network (ODN). A PON system may be: Gigabit Passive Optical Network (GPON, namely, 2.5 Gbps PON), 10-Gigabit Passive Optical Network (XG-PON, namely, 10 Gbps PON), Ethernet Passive Optical Network (EPON), ATM Passive Optical Network (APON), or Broadband Passive Optical Network (BPON).
In a PON system, because the transmission distance of fibers is up to scores of kilometers or even over a hundred kilometers, the distance from a PON port to ONUs under this PON port varies sharply. To prevent deterioration of services, communication protocols generally restrict the distance difference between ONUs under the same PON port. For example, in a GPON system, the protocols specify that the upper threshold of the distance difference between ONUs under the same PON port is 20 km.
In the process of implementing the present invention, the inventor finds at least the following defects in the prior art:
The application scope of the PON is wider; in specific application environments, the distance difference between ONUs under the same PON port is restricted so that the operator has to provide independent PON ports for users located at different distances, which brings an adverse effect on reasonable use of port resources; moreover, inefficient running of devices leads to a high cost of maintenance and hinders energy saving and emission reduction.